How can I get the geographic coordinates of a place just by entering the addresses in input? on c # I searched the internet but could not find information for c #
You need to use an API such as Googles Geocoding API: https://developers.google.com/maps/documentation/geocoding/
But beware, the licence says the results must be displayed on a map!
If that's a problem, I'd look at the others in Mathew Watson's link: http://github.com/chadly/Geocoding.net